An introduction to the
Web of Things Framework
May 2015
Dave Raggett, W3C
This work is supported by the European Union's 7th Research Framework
Programme (FP7/ 2013-2015) under grant agreement nº317862 - Compose
The Promise of the IoT
With thanks to Vision Mobile
The Challenge
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We expect one hundred billion IoT devices to be deployed
within ten years
But, the Internet of Things is currently beset with problems
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Product silos that don't interoperate with each other
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Plethora of approaches & incompatible platforms
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This is blocking the benefits of the network effect
This is painful for developers
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Hard to keep track of who is doing what
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Expensive to learn and port to different platforms
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Challenging to create services that span domains and platforms
Platform developers seeking to unlock the commercial potential
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To reduce development costs for IoT applications and services
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To fulfil customer demand for services requiring integration with other platforms
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To grow the size of the overall markets
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A small share of a huge market is better than a big share of a small market
3/26
The Web as the Solution
“Things” as virtual objects acting as proxies for physical and abstract entities
**
4/26
Many Business Opportunities
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Homes & Offices
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Life and Healthcare
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Security, Energy, Entertainment, Pets, Lighting, Heating (HVAC), White Goods, ...
Fitness, monitors, medication
Cities
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Transportation, Utilities, Planning, Security
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Energy
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Reducing peak demand through smart energy appliances
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Dealing with local generation of power, and rise of electric cars
Retail & Catering
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Logistics, Design, Manufacturing
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Reduction of 1% of operational costs can save billions
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Speeding design to delivery of bespoke products
Environment
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Logistics, Beacons, Richer information on products, Loyalty schemes
Industry
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Cars as an integral spart of the Web of Things
Droughts, Floods, Fires, Emergency management
Big Data
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Creating value by analysing combinations of multiple sources of data
5/26
From Pages to Things
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The web of pages is founded upon
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IRIs for addressing
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HTTP for access
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HTML for pages and for discovery
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Search engines following the links in pages
Web of Things by analogy with web of pages
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IRIs for addressing
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HTTP and other protocols for access
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No one protocol can satisfy all needs
Thing Description Language (TDL)
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Semantics and data formats as basis for interoperability
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Relationships to other things as basis for discovery
** IRI is an abbreviation for Internationalised Resource Identifiers (aka URIs or web addresses)
6/26
Web of Things Framework
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Expose IoT platforms and devices through the
World Wide Web for a Web of Things
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Device abstraction layer to bridge IoT to the Web
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“Things” as proxies for physical and abstract entities
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Modelled in terms of events, properties and actions
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What events does this thing generate?
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Someone has just rung the door bell
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Someone has just inserted a door key
What properties does this thing have?
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What actions can we invoke on this thing?
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Door is open or closed
Unlock the door
Thing with on/off property as proxy for a light switch
With bindings to scripting APIs and protocols
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Service logic decoupled from underlying communication details
7/26
Web of Things Framework
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Standard way to retrieve “thing” descriptions
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Standard format for “thing” descriptions (e.g. JSON-LD)
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Owner, purpose, version, access control, terms & conditions,
relationships to other things, security best practices, . . .
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Semantics and data formats for events, properties & actions
Properties have discrete values, or smoothly changing values
that are interpolated between data points, e.g. for robotics
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Delegating control to where it makes the most sense
Clock sync across controllers: 1-10 mS with NTP,
and microseconds with IEEE protocols
Communication patterns
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Giving data owners control over who can access their data
and for what purposes – contract between consumer & supplier
Push, pull, pub-sub, and peer to peer
Bindings to a range of protocols
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HTTP, Web Sockets, CoAP, MQTT, STOMP, XMPP, WebRTC
8/26
Interacting with a “Thing”
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Representational State Transfer (REST)
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HTTP GET to retrieve a thing's description
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HTTP GET to retrieve all properties of a thing
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HTTP PUT to update all properties of a thing
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HTTP PATCH to apply changes to some properties
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HTTP POST to invoke actions on a thing
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HTTP POST is also used to notify events
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To proxies or dependent things
REST can be used with other protocols
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To send actions to thing within a firewall
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To distribute updates via pub-sub model
9/26
Servers at many scales
Servers are free to choose which scripting languages they support
Could precompile service behaviour for constrained devices
10/26
Example of a Home Hub
11/26
Relationships between Things
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“Thing” description includes the relationships to the things that this
thing depends upon
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Server uses this to retrieve descriptions of related things as basis for
deciding how to connect to them and expose them to scripts that define
this thing's behaviour
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With support for circular dependencies
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Enables search engines to index the web of things
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Supports richer search queries based upon relationships
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Enables dependency management
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Perhaps analogous with Linux package management
Decouples service behaviour from data protocols
Simpler expression of service behaviour via
local names for things
Choice between early and late bound types
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Strong vs weak typing and implications for extensibility
12/26
End-User Service Creation
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Event-condition-action rules
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Trigger action upon event if condition is true
High level events defined in terms of
lower level events
Higher level actions defined in terms of
lower level actions
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Ordered and unordered sequences of actions
Pre- and Post-conditions
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Simple to use graphical editing tools
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Vocal commands (as with Apple's Siri)
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“turn the heating down when I leave home”
13/26
Appeal of JSON-LD
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What makes JSON-LD attractive as basis for the thing description
language?
W3C Recommendation from 16 Jan 2014
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Combines simplicity of JSON with the power of the Linked Data and
the Semantic Web
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http://www.w3.org/TR/json-ld/
Out of band profiles and binary JSON formats for short packet protocols
We would define a core profile for a vocabulary common to
all “thing” descriptions
Implementers would be encouraged to re-use vocabularies for
specific application domains
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These could be defined by industry specific groups
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Need for better schema/vocabulary languages?
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Dynamic data validation for greater robustness
14/26
Thing Descriptions
Server uses IRI for a thing to download its description
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{
}
Door
“@events” : {
“bell”: null,
“key”: {
“valid” : “boolean”
}
},
“@properties” : {
“is_open” : “boolean”
},
“@actions” : {
“unlock” : null
}
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{
}
Light switch
“@properties” : {
“on” : {
“type” : “boolean”,
“writable” : true
}
},
TDL's default JSON-LD context defines bindings of core vocabulary to IRIs
Data models may be defined explicitly or by reference to an external definition
Thing as Agent
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Thing description
{
}
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It's behaviour
// invoked when service starts
@context : {
@base=”http://….
},
“@dependencies” : {
“door” : “door12”,
“light” : “switch12”
}
function start () {
door.observe(“key”, unlock);
}
function unlock(key) {
If (key.valid) {
door.unlock();
light.on = true;
}
}
This “thing” is an agent that is bound to a specific door and light switch.
It unlocks the door and turns on the light when a valid key is presented.
n.b. @base defines a base IRI for resolving relative IRIs
Miscellany
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For validation and specification of vocabularies
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JSON-Schema
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RDF-Schema
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OWL
For efficient transfer of structured data
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JSON (defined by RFC7159, ECMA 404)
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Google's Protocol Buffers
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XML with EXI
Bindings to protocols need to cover encodings
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MessagePack, Universal Binary JSON, etc.
/.well-known/protocols for retrieving server's protocol support?
Actions on things are asynchronous and may return results
Thingsonomies
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The purpose of a “thing” can be defined formally in respect
to an ontology
The purpose can be defined informally using free text, e.g.
as one or more tags chosen by the maintainer
Co-occurrence of tags across many “things” performs an
informal expression of semantics
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In same way as folksonomies for images or blog posts
Statistical treatment of natural language and cognitive
models make this increasingly attractive, e.g.
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Apple Siri
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Google Now
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IBM Watson
Thing Descriptions
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Thing descriptions may be static and shared by many “things”
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These things can define their description by reference
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Relationship to statically typed programming languages
Some kinds of things may involve descriptions that change over
time, e.g. a new owner, or a new physical location for a sensor
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Events signalling changes to metadata?
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Thing memories that record changes over a thing's lifetime
Bindings to protocols may involve self tagged data
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Analogous to “unions” in programming languages
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Allows for extensibility – ignore new fields you don't know about
The properties of a “thing” may include data blobs that have a
meaning and a content-type
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Photo of someone and encoded as image/jpeg
Focus of W3C Contribution
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Things
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Thing descriptions
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Data models & relationships between things
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Dependencies and version management
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Discovery and provisioning
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Bindings to APIs and protocols
Security related metadata
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Security practices
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Mutual authentication
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Access control
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Terms & conditions
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METADATA
Security
Comms
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Relationship to “Liability”
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Payments
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Trust and Identity Verification
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Privacy and Provenance
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Resilience
Communication related metadata
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Protocols and ports
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Data formats & encodings
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Multiplexing and buffering of data
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Efficient use of protocols
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Devices which sleep most of the time
20/26
Semantics for Smart Appliances
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Semantic Sensor Network Ontology
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W3C SSN Incubator Group report
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SSN Ontology
Sensor Model Language (SensorML)
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Sensor Markup Language
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Developed by Open Geospatial Consortium
JSON & XML/EXI – IETF draft-jennings-core-senml
TNO's smart appliance ontology for ETSI M2M
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Developed on behalf of European Commission
IETF CoRE WG
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CoRE WG with focus on resource oriented applications for
constrained IP networks, and responsible for CoAP protocol
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See tracker page and CoAP website
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CoAP is based on REST and similar to HTTP
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GET, PUT, POST, DELETE, OBSERVE methods
CoAP is a good fit for the Web of Things
Resource discovery
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Unicast or multicast queries
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Link format (RFC6690) analogous to HTTP Link header
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Which itself is modelled on HTML's LINK element
JSON link format under consideration
GET /.well-known/core returns list of resources
Notifications with push and pub-sub
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Interested parties register with GET
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Notifications are sent with OBSERVE method
The Maker Community
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Open hardware and open source software are a huge
opportunity for a bottom up approach to growing the
Web of Things
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Let's have lots of fun!
ESP8266: 80MHz
32 bit MCU + WiFi
Available for 2 USD
Arduino
CoAP: REST for IoT devices
MicroCoAP: 16 KB including the
Ethernet library, for more see:
https://github.com/1248/microcoap
MQTT as a lightweight binary
Pub-sub protocol with brokers, see:
https://github.com/knolleary/pubsubclient
NodeJS based Web of Things server
with many libraries available for IoT
(run on Raspberry Pi as Home Hub)
CC2530: 8051 MCU + IEEE 802.15.4
Up to 256 KB flash + 8 KB RAM
Available at 0.5 USD in quantity
C & Arduino IDE
Lua & NodeMCU
MicroPython
RIOT OS
Sensors
Web of Things Interest Group
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Launched in January 2015
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Focus on pre-standardisation work
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First face to face in Munich, April 20-22
Survey of use cases and requirements across
app domains and business sectors
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Architecture and technology landscape
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Security, privacy and resilience
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Discovery and provisioning
Liaison with external IoT groups
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See list on IG wiki page
Preparation of proposed WG charter for launch late 2015
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Standardise Web of Things Description Language
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Standardise Bindings to APIs and Protocols
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In collaboration with other groups
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IETF protocols such as HTTP, WebSockets, CoAP, and XMPP
Security best practices
24/26
Join the Web of Things IG
http://www.w3.org/WoT/IG/
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Help us to prepare the ground for standardizing the Web of Things
Framework by joining the Interest Group
We've recently set up the following task forces
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Use cases and requirements
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We're looking for help with broadening this
across a wide range of business sectors
You can help us to set up task forces for
specific business sectors
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Web of Things Framework
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How much money could your company benefit from the IoT?
Thing descriptions
Discovery and provisioning
Bindings to APIs and protocols
Security and Privacy
We plan to review a draft Working Group charter
at our July F2F in North America
25/26
Summary
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The IoT is growing very fast but needs web scale standards to realise its potential
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The Web of Things is based upon Linked Data to model virtual objects as proxies for physical
and abstract entities
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Web technologies to enable web scale markets and reduce the cost for developing IoT apps and services
JSON-LD combines simplicity of JSON with the power of Linked Data
A new class of web servers that communicate with each other at
an abstract level in terms of metadata, events, properties and actions
Bound to a variety of protocols to support common communication patterns
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Push, pull, pub-sub and peer to peer
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Protocols like HTTP, WebSockets, CoAP, MQTT, XMPP and WebRTC
Implementable on a wide range of scales
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Microcontrollers with CoAP
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Smart phones and home/office hubs
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Cloud-based server farms
Supports early and late bound data types
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Important for extensibility and resilience to changes
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W3C WoT IG on pre-standardisation activities, WG to follow late 2015
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Help us to enable the IoT to realise its full potential!
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